Power hammer



Jan. 12, 1932.

W. F. TROTTER POWER HAMMER Filed March 16 1929 :5 Sheets-Sheet 1 a; 4 iI 1% l'l q 64 W lwnonueu Jan. 12, 1932; w. F. TROTTER POWER HAMMER 3Sheets-Sheet 2 Filed March 16, 1929 I77 Md ATTORNEY,

Jan. 12, 1932. w. F. TROTTER POWER HAMMER Filed March 16, 1929 3Sheets-Sheet 3 INVENTOR WATTORNEY Patented Jan. 12, 1 932 UNITED STATESPATENT OFFICE WALTER F. TROTTER, OF CINCINNATI, OHIO, ASSIGNOR TO THEOHIO ELECTRIC HAM- MER CORPORATION, A. CORPORATION OF OHIO POWER HAMMERApplication filed March 16, 1929. Serial No. 347,668.

This invention relates to power driven improper placement of the anvilor tool head hammers or drills for breaking pavement and with resultantbadly timed impact, the objecconcrete surfacing or drilling the same bytive here being a uniform deceleration or localized impact andintermittent rotation of cushioning to a complete stop and retraction 5the tool, and is particularly directed to an without detriment to themechanism or shock 5 improved mechanism for converting rotary to theoperator, smoothing out the driver motion into reciprocatory motion forimaction' by merging and checking the recoil pacting the, tool, and to amechanism for rapmovement in the retraction actuation of the idly andaccurately intermitting rotation of ram.

the tool for alternate rotation and impact. Another object is to providein this type 60 The'motion converting mechanism is in of ram actuatingdevice a yieldability of; the form of a driven cam device having twoContact between the ram and the actuating cam surfaces, the camreciprocating a ram or means. driver by alternateengagement with the reAnother object is to provide an improved spective cam faces, and thecamsurfacesmade mounting for the ram or driver for hig .yieldable underimpact or ram engagement. velocity reciprocation. One cam face is formedwith a portion of -An intermittent motion device is provided sharp curvefor initially imparting a high and inserted in conjunction with theforevelocity impulse to the ram, directing it togoing device forintermittent rotation of a 0 ward an anvil or head end of the tool, anddrill impacted by the ram, and this device is the other cam face is socleared in the adjaincorporated as a part of a worm and worm rentportion that there will be no engagegear transmission inserted betweenthe cam ment of the ram with the first cam surface to driving shaft andthe drill. interfere with the sudden impact. There- The provision ismade, to accomplish this fore, as induced by this cam impulse, theresult, of a worm havingathread of varying 75 ram moves of its ownmomentum against the pitch, by means of which a part'revolution toolanvil andimpartsaheavy impact thereto. of the Worm advances the wormWheel one The ram and tool anvil are so related that the tooth. Thepresent invention utilizes the impact comes during the free movement ofremainder of a particular thread convolution the ram. If the tool is notin position as as the idling period for the worm gear. This 30 mightoccur, due to the rapid hammering, oris accomplished by terminating therise or the fact that the tool was not held firmly pitch of theth'readupon a part revolution, against the work, theram is decelerated by andcontinuing the remainder in a plane at 3! engagement with auniformlycurved portion right angles to the axis of the worm and 0 of the firstcam, this portion straightening therefore with no p tch. The part of theout into a horizontal, and uniformly curving thread having no pitchmerely passes bel'n a reverse direction to slowly retract-the tween theteeth of the worm gear wlthout ram for the next succeeding blow.rotating effect until the ad o1ning convolu- 4 It is therefore an objectof this invention to tion is'engaged. As long as a lead or use provide adevice for reciprocating the ram of a particular convolution of the wormor driver of the machine for impacting a tool, thread is sufficlent toadvance the worm gear which device initially sharply and uniformly aleast one ooth,'the rem in er of he conaccelerates the ram in downwardmovement volution may be straight or even of negative andthereafterreleases the same, permitting pitch, the latter being of utility whenoscillas 9 it to strike the tool head or anvil under the tion of a gearis desired. 5

influence of its own momentum. It is, therefore, another object of thisin- It is another objectto provide for eflicient vention to provideintermittent rotary modeceleration of the actuated ram moving untion bymeans of a continuously meshing o der the normal, high, necessaryvelocity parworm and worm gear. Um ticularly when there is a failure ofimpact or It is further-provided that the teeth of the worm gear arestraight out in part "and diagonally cut in part so that theworkingsurfaces of said teeth are smoothly engageable either by thepitch portion of the worm thread or by the straight portion thereof.

Another object of this invention is to efficiently synchronize theaction of the drill impacting device and the intermittent 'rotativemotion device to insure intermittent impact and rotation of the tool.

Further objects and advantages will be more fully set forth in thedescription of the accompanying drawings, in which:

Figure l is a perspective view of'a concussion or drilling apparatusembodying the features of the present invention.

Figure 2 is a central sectional view taken longitudinally of theapparatus.

Figure 3 is a transverse sectional view taken on line 33, Figure 2,illustrating the fan for cooling the motor.

Figure 4 is a sectional view taken on line 44, Figure 2, illustratingthe guided mounting of the ram in the frame. Figure 5 is a sectionalview taken on line 5-5, Figure 2, showing the relatiqn of thecam to theram.

Figure 6 is 'a transverse sectional view taken on line 66, Figure 2,illustrating the transmission for intermittently rotating the anvil fromthe cam shaft.

- Figure 7 is an enlarged side elevation of the cam removed from themachine.

Figure 8 is a diagrammatic or developed view illustrating. the camlayout and relation of the respective cam surfaces.

Figure 9 isan enlarged detail view of the worm' and worm gear used forimparting intermittent rotation to the anvil.

Figure 10 is a side elevation of Figure 9.

Figure 11 isa diagrammatic view or development of the thread of theWorm.

The apparatus embodying the features of the present invention is shownin the nature of a portable electrically driven concussion or drillingdevice. It embodies, in general, a power source as an electric motormounted in the upper endthereof, the motor driving a cam shaft throughan appropriate speed reduction gearing, and the cam shaft extendinglongitudinally of the normally vertically extending body of theapparatus and j ournalled in the respective ends thereof.

The concussion device primarily comprises a doublefaced cam having theadvantages previously outlined, and the cam in operative engagement witha guided ram. or driver, this ram or driver being disposed "forreciprocal motion longitudinally of the body of the device. Below theram and in alignment therewith an anvil is disposed in the frame.

.In the case of the drill, the anvil is mounted for rotation and isrotated by means of a gearing-arrangement from the cam shaft, the anvilbeing in slide connection With its rotabreaking tool being used aconveniently manipulated attachment device is used for afiixing the toolto the frame relative to the anvil.

Referring to the drawings, the frame of thedevice is made up of a motorcasing 15, a driver and operating means casing 16, and an anviltransmission casing 17, these casings secured together in verticalrelation. Handles indicated at 15 are provided on the casing, one at thetop and one extending laterally therefrom. A rotor or armature 18isvertically journalled in the motor casing and has its shaft 19 1extending downwardly through a lower bearing 20 and a pinion gear 21secured on the extending end. A hearing plate 22 is secured between theupper or motor casing and the intermediate or ram casing, this platehaving the bearing 20 secured therein journalling the lower end of themotor shaft and also a bearing 23 journalling the upper end of a camshaft 24. The cam shaft 24 extends longitudinally within theintermediate casing and isjournalled in the lower or anvil transmissioncasing.

A fan 25 is secured on the motor shaft between thebody of the motor andthe bearing plate, the air circulation being through apertures 26 in thelower portion of the side walls of the motor casing and apertures 26 inthe top wall thereof. -A gear 27 is keyed to the cam shaft and is inmesh with the pinion 21 of the motor. a

- The driver cam 28 is keyed to the shaft intermediate the shaft length,being maintained against longitudinal displacement by means of acollar29 engaging lts lower hub and holding it against a spacer sleeve30 fixed to the shaft 24 between its upper hub and the gear 27. The camis sectional, the sections 31, 32, thereof each having peripheralflanges oppositely disposed, the surfaces of the flanges being the ramactuating and controlling mediums as hereinafter described. The cams areyieldingly spaced apart by means of a coil spring 33 under compressionseated in deepconcentric grooves 34 in the opposing faces of thesections. The co-related peripheral flanges of the cams pass between apair of rollers 35-35 mounted on the vertically reciprocably mounted ram36.

V The ram is vertically guided between pairs of ball bearing rollers 37,a pair ateach side thereof, these ball bearing rollers engaging ingrooves 38 longitudinally formed in the side walls of the ram and beingjournalled in the side walls of the casing. The journalling of the ballbearing rollers is by means of headed studs 39 passing through the sidewall of the casing and rigidly held in position by means of nuts 40,there being an intermediate shoulder 41 on the shank of each studengaging the inner side of bushings fixed in the casing wall andpreventing clamping of the inner ring of the ball bearing rollers, thisloose mounting of the inner bearing ring permitting greater freedom ofmotion of the ram. The ram is floatingly guided for reciprocal motion inthese ball bearing connections for reducing the friction and allowingthe ram to move with a maximum of freedom, and when released from theinfluence of the cam moves under its own momentum for impact with thetool.

An anvil or impact transmitting bar and spindle 42 is mounted inalignment with the ram and has its upper end positioned for impact bythe ram. The anvil has a hexagon shaped upper end 43 for rotativeconnection with a sleeve 44 rotatively j ournalled in bearings 45secured in the transmission casing. The anvil extends through adownwardly disposed boss 46 of the casing and has a chuck 47 formed onits lower end.

A retainer sleeve 48 is screw-threaded onto the lower end of the bossand has an inwardly extending abutment flange 49 at its lower end. Anannular shoulder 50 is formed on the chuck portion of the anvil and isadapted to engage the inwardly turned flange, this inwardly turnedflange 49 being spaced away from the lower end ofthe boss, and theannular shoulder of the anvil engaging therewith prevents the anvil fromdropping from the device. The spacing of the inner flange from the endof the boss 46 is suflicient to permit the unhampe'red movement of the.

anvil under the impacts of the concussion device. i

A drill 51 is socketed in the chuck in the 4 conventional manner andengagement of the ram at the beginning of a cycle. The cam' moving tothe left, as viewed from the ram side, presents a sharply curved lowercam surface 52 which engages the lower roller of the ram and impartsdownward movement to the ram.

If the anvil is properly positioned, the impact of the ram with the toolcauses the ram to dwell in the position of impact where the slowlyrising surface 53 of the upper cam comes smoothly into engagement withthe upper roller of the ram and retracts the driver for the succeedingblow.

It will be apparent from Figure 8, that after the ram has departed fromengagementwith the lower cam, the distance between the upper and lowercam surfaces decreases materially so that there is considerableclearance for the ram to move in, prior to engagement of the upper orreturn cam surface 53 with the upper roller.

1t frequently happens that the anvil is not in exact position to receivethe impact or concussion, this occurring when there is chattering ofthetool or when the tool is not held firmly against the work. For thisreason, the upper cam surface is provided with a portion 54 adjacent thepoint of departure 55 on the lower cam which is designed to engage theupper roller of the ram, this portion 54 being of uniform cury e to ahorizontal to slowly andsmoothly decelerate the ram in its downwarddirection in the event of failureof impact. This decelerating surfacesmooths out into a horizontal and then rises to represent the previouslydescribed slow rising surface 53 for retracting the ram. The ends of thedeveloped view represent the beginning of.

the cycle, being taken at a coincidental line on the cam.

The throwing cam 32 has its throwing face shaped to give theram auniformly accelerated motion downwardly. or in a direction to impactwith the tool which continues while the ram is in contact with thethrowing face. After leaving the throwing face of the cam 32 the ram isfree to continue for a limited distance under the influence of its ownmomentum. It is during this period the impact with the tool or anviltakes place. If the weight relation between the ram and tool is correct,the ram comes practically to rest and remains so until contact is madebetween the ram and the upper or returning cam. The surface 54 of theupper cam 31 from the point or end of the throwing face of the throwingcam 32 continues to recede and with the rotation of the cam provides forthe free motion of the ram for impact with the tool and comes to restbefore again acted upon by the cam or the upper cam 31. The recedingportion of the upper cam also serves to give the ram a uniformnegativeacceleration or gradually retards the downward motion of the ram if thetool is not in position to stop or receive the impact. This actioncontinues with the rotationof the cam until the ram is brought to restby non-ram moving portion of the upper cam, whereupon the surface of theupper cam ascends to move the ram in an opposite direction.

The two cams. aresplined upon the shaft with the spring under tensioninterposed between the cams pressing each cam inthe direction in whichthe cam throws or moves the ram. Each cam, therefore, is capable ofyielding motion or automatic adjustment to relieve it of sudden shocksinterposed thereon when coming into engagement with the ram either at apoint at which one of the cams decelerates the motion of the ram orcounter acts the motion of the ram. The cams can thus be made separatelyfacilitating in their manufacture. The cams are loosely keyed upon theshaft with their cam faces outwardly and stops placed on the shaft,spaced a distance apart slightly greater than the combined length of thecams along the shaft. The spring interposed between two cams serves tocushion the cams.

intermittent motion is imparted to the rotatively mounted sleeve 44,which is in rotative connection with the anvil, by means of a crossshaft 64 journalled in'the side walls of the frame. A worm 65 is pinnedto the cam shaft 24 at its lower end, this worm beingin engagement witha worm wheel 66 keyed to the cross shaft. At the other end of the crossshaft 64 a worm 67 is keyed thereto and properly spaced thereon by meansof spacer sleeves 68 for meshing with a worm wheel 69 keyed to the anvilsleeve 44. 1

It is the particular formation of these last mentioned .worm and worm'gear elements which provides the intermittent motion. The

Worm of this combination is shown as of a.

single thread formation. The pitch. of the worm is variedand half of aconvolution thereof is devoted to a gear turning pitch and the otherhalf is a straight thread for idling of the worm wheel. I

Regarding a given thread, as shown in the developed view Figures 9 and11, the thread has a pitch for one-half convolution as at 70, and thenis straightened out to a plane at right angles to the axis of the wormfor a half convolution as at 71 where it joins the next pitch or riseportion. By utilizing half a convolution of thethread spiral for thelead, the worm wheel is advanced-one tooth and the remainder of therevolution is devoted to a dwell. i 4

Due to the fact of the use of a worm of this nature the thread presentedto the worm gear is at varying angles, that is to say, at the angle ofthe desired pitch or at right angles to the axis of the worm. The teethof the worm wheel are therefore cut or milled see F i re 10) parallelwith the axis thereof as and also aim. tangent as at 73, the'angle oftangent corres onding to the pitch of the worm thread. T is providesteethedges always in substantial driving engagement with the thread ofthe worm.

Another variation of the lead, which may be used, is of the ensuingnature. If the driving lead or pitch of each convolution is of greaterlength than is necessary for advanc- ,ing the worm wheel one tooth, theexcess advance of the worm wheel over the one tooth, requirement couldbe reversed by giving the remainder of the convolution a reverse ornegative lead equal to the excess.

It can be seen that by this arrangement the motion of the worm wheelcould be made forward and stationary for each revolution orconvolutionfof the worm, or it could be made forward and backward, or itcould be made forward, stationary and backward, provided, however, inall instances the restriction of having an advance. of the 'worm wheelone tooth. The excess beyond that could be varied in any manner asaforesaid.

By properly positioning the cam on the cam shaft and relating thetransmission thereto, the impact is given to the anvil While thestraight portions of the worm are in mesh so that the rotative dwellcomes when the impact is being delivered. This synchronizatibn is highlydesirable for a drill since the turning of the drill at the moment ofimpact would unduly wear or break off the sharpened edges thereof.

Having described my invention, I claim:

1. In a tool of the class described, a ram floatingly supported forreciprocal motions for impact with a cutting tool, and a pair of camssplined.upon an axis and rotatable as a unit, one for moving the ram inone direction and the other in a reverse direction, said camseach-yieldable in a direction counter to the direction in which it movesthe ram.

2. In a tool of the class described, a ram, floatinglyrs upported forreciprocal motions for impact with a cutting tool, a pair of camsrotatable as a unit, one for moving the ram in one direction and theother in a reverse direction, and means for yieldingly urging said camsin opposite directions axially, said means taking up the shocks when thecams respectively become effective upon the ram with the reversal ofstrokes. f

In witness whereof, I hereunto subscribe my name. r

" WALTER F. TROTTER.

